JPWO2018003547A1 - Heat conduction sheet and secondary battery pack using the same - Google Patents

Abstract

It is an object of the present invention to provide a thermally conductive sheet which can be easily bonded from one surface of a battery cell to another surface orthogonal to the surface. It is a heat conductive sheet (11) sealed by sandwiching the entire graphite sheet (12) with an insulating sheet (13). A plurality of notches (14) are linearly arranged in the graphite sheet (12), and the battery cell is formed by bending the heat conductive sheet (11) in the area of the notches (14). It is made to be able to bond from one side to another orthogonal side.

Description

  The present disclosure relates to a heat conductive sheet used for a lithium ion secondary battery and the like, and a battery pack using the same.

  Lithium ion secondary batteries have come to be mounted on various devices, and their current capacities have also increased. As the current of lithium ion secondary batteries increases, the importance of heat countermeasures for lithium ion secondary batteries is becoming increasingly important. A lithium ion secondary battery is usually used as a battery module by connecting a plurality of battery cells. When the temperature difference inside the battery cell of the lithium ion secondary battery becomes large or the temperature difference between the plurality of battery cells becomes large, the deterioration of the lithium ion secondary battery tends to proceed. Therefore, in order to prevent the deterioration of the lithium ion secondary battery, it is important to take measures against soaking in the battery cell. Therefore, many techniques arrange a heat conductor in the battery module to equalize the temperature of the battery cell. It is practiced to use a graphite sheet as this heat conductor.

  For example, Patent Document 1 is known as prior art document information related to this technology.

JP, 2015-71727, A

  When a heat conductor is used, it is desirable to provide an adhesive on the surface in contact with the heat generating body to bring it into close contact with the heat generating body in order to efficiently transfer heat. When the heat conductor is used in a small electronic device such as a mobile phone, the graphite sheet is also small, so there is no problem in bonding. However, in the case where the heat conductor is attached to a large one such as a battery cell for vehicles, it is necessary to use a graphite sheet having a large area. Further, in order to make the temperature of the battery cell uniform, it is sufficient to bond the heat conductive sheet only to the side surface having the largest area. On the other hand, in order to lower the temperature of the battery cell, it is desirable to extend the heat conductive sheet from the side surface to a surface in contact with the casing, such as the bottom surface. Graphite sheets are conductive. Therefore, an insulation sheet is usually pasted together on both sides of a graphite sheet, and the graphite sheet which pasted this insulation sheet is used as a heat conduction sheet. Thus, since it becomes difficult to bend the graphite sheet having the insulating sheets bonded on both sides, when bonding is attempted from one surface of the battery cell to another surface perpendicular to the surface, it is difficult to perform bonding such as swelling at corner portions.

  The present disclosure is a thermally conductive sheet in which the whole of a graphite sheet is sandwiched and sealed by an insulating sheet in order to solve the above-mentioned problems, and a plurality of notches are linearly arranged in the graphite sheet. It is something that

  By doing so, the heat conductive sheet can be easily bent in the area of the notch, and the heat conductive sheet can be easily bonded from the side surface to the bottom surface of the battery cell.

Top view of the heat conductive sheet in the first embodiment of the present disclosure The II-II sectional view shown in Drawing 1 of the heat conduction sheet The III-III sectional view shown in FIG. 1 of the heat conductive sheet Cross section according to a preferred example of the same heat conductive sheet Partial cross-sectional view of the heat conductive sheet in the first modification Partial cross-sectional view of the heat conductive sheet in the second modification Partial cross-sectional view of the heat conductive sheet in the third modification Partial cross-sectional view of the heat conductive sheet in the fourth modification Partial top view of the heat conductive sheet in the fifth modification Partial top view of the heat conductive sheet in the sixth modification Partial top view of the heat conductive sheet in the seventh modification A perspective view of a battery cell in a second embodiment of the present disclosure The line VIII-VIII sectional view shown in FIG. 7 of the same battery cell Schematic of the battery pack Top view of the heat transfer sheet in the third embodiment of the present disclosure Perspective view of the same battery cell The line XII-XII sectional view shown in FIG. 11 of the same battery cell Schematic of the battery pack The figure which shows an example of the method of sealing of the graphite sheet concerning this indication. The figure which shows another example of the method of sealing of the graphite sheet concerning this indication.

First Embodiment
Hereinafter, the heat conductive sheet in the first embodiment of the present disclosure will be described with reference to the drawings.

  FIG. 1 is a top view of a heat transfer sheet 11 according to a first embodiment of the present disclosure. FIG. 2 is a cross-sectional view of the heat conductive sheet 11 shown in FIG. 1 taken along a line II-II and cut by a plane perpendicular to the paper surface. FIG. 3 is a cross-sectional view of the heat conductive sheet 11 shown in FIG. 1 cut along a line III-III in a plane perpendicular to the paper surface. The II-II line is a line along the arrangement direction of the notches 14 including the plurality of notches 14, and the III-III line is perpendicular to the II-II line passing through one notch 14. Is a line extending in the

  The heat conductive sheet 11 is constructed by laminating, for example, one insulating sheet 13 of about 10 μm in thickness made of polyethylene terephthalate (hereinafter referred to as PET) on both sides of a graphite sheet 12 of about 50 μm in thickness. ing. On the surface of the insulating sheet 13 facing the graphite sheet 12, for example, an adhesive (not shown) made of an acrylic resin is provided. The insulating sheet 13 and the graphite sheet 12 both have a rectangular shape. The insulating sheet 13 has a larger shape than the graphite sheet 12. The graphite sheet 12 is sealed by adhering the insulation sheets 13 in the portion where there is no graphite sheet 12 at the end of the insulation sheet 13 with an adhesive. The graphite sheet 12 is formed, for example, by thermal decomposition of a polymer film.

  In the graphite sheet 12, a plurality of notches 14 each having a rectangular shape and penetrating the graphite sheet 12 are arranged in line in a straight line. The length in the direction in which the notches 14 are arranged is L, and the length between the notches 14 and the notches 14 is S, L = 10 mm and S = 5 mm. Moreover, in the inside of this notch part 14, insulation sheet 13 comrades are adhere | attached by the adhesive material. A recess 16 is formed on one side of the adhered insulating sheet 13 in correspondence to the notch 14.

  In the thermally conductive sheet 11 in which the insulating sheet 13 is bonded to both surfaces of the graphite sheet 12 in which the plurality of notches 14 are linearly arranged as in the present embodiment, the heat conduction sheet 11 is along the notches 14 It can be easily bent with a line. Therefore, bonding of the heat conductive sheet 11 to the battery cell can be facilitated, for example. Since the graphite sheet 12 is excellent in thermal conductivity in the surface direction, heat can be sufficiently conducted in portions other than the notched portion 14 even if the notched portion 14 is present. Therefore, when the graphite sheet 12 is bonded to the battery cell, heat can be transmitted from the side surface to the bottom surface and dissipated through the housing.

  The length L between the notch 14 and the length between the notch 14 and the notch 14 is S. At this time, the relationship between L and S,

It is more desirable to When L / (L + S) is smaller than 0.5, the bendability may be slightly deteriorated, and conversely, when it is larger than 0.9, the thermal conductivity is easily inhibited.

  When the width of the notched portion 14 in the direction perpendicular to the direction in which the notched portions 14 are arranged is W, the thickness of the graphite sheet 12 is T1, and the thickness of the insulating sheet 13 is T2,

It is more preferable to When W is smaller than 2 · (T1 + 2 · T2), it becomes difficult to bend, and when it is larger than 10 · (T1 + 2 · T2), the strength is easily deteriorated and the thermal conductivity is easily inhibited. In the heat conductive sheet 11, T1 ≒ 50 μm and T2 ≒ 10 μm.

  In addition, as shown in FIG. 2, it is desirable that the insulating sheets 13 be joined to each other inside the notch portion 14. Furthermore, as shown in FIG. 4, it is more preferable that a through hole 17 be formed instead of the concave portion 16 in the insulating sheet 13 inside the notch portion 14. By forming the through holes 17, air can be released from the through holes 17 even if air is taken in, for example, at the time of bonding to the battery cells, and the heat conduction sheet can be closely attached to the battery cells. 4 is a cross-sectional view corresponding to the cross-sectional view shown in FIG.

  About the cross-sectional shape in the notch part 14 of the heat conductive sheet 11, and its vicinity, it is possible also in the case of the following modifications 1-4. Moreover, about the upper surface shape in the notch part 14 of the heat conductive sheet 11, and its vicinity, it is possible also in the case of the modifications 5-7.

(Modification 1)
The shape shown to FIG. 5A is also possible as a cross-sectional shape in the notch part 14 of the heat conductive sheet 11 concerning the modification 1, and its vicinity. In FIG. 5A, in the insulating sheet 13 on the other of the two insulating sheets 13 to be bonded, a recess 18 is provided at a location corresponding to the notch 14. The other configuration requirements are the same as in the case of FIG.

(Modification 2)
As a cross-sectional shape in the notch part 14 and its vicinity of the heat conductive sheet 11 concerning the modification 2, the shape shown to FIG. 5B is also possible. In FIG. 5B, a triangular groove 19 is provided in a portion corresponding to the notch portion 14 of one of the two insulating sheets 13 to be bonded.

  The other insulating sheet 13 may have a flat shape without the depression 18 at a location corresponding to the notch 14.

  In addition, the insulating sheet 13 may be penetrated through the triangular groove 19. In this case, even if air is taken in when the heat conductive sheet 11 is attached to, for example, a battery cell, air can be released from the groove 19 and the heat conductive sheet 11 can be closely attached to the battery cell.

(Modification 3)
As a cross-sectional shape in the notch part 14 of the heat conductive sheet 11 concerning the modification 3, and its vicinity, the shape shown to FIG. 5C is also possible. In FIG. 5C, of the two insulating sheets 13 to be bonded, one of the insulating sheets 13 is provided with a slit 20 at a position corresponding to the notch 14. The slit 20 is formed by providing a cut in the insulating sheet 13.

  The other insulating sheet 13 may have a flat shape without the depression 18 at a location corresponding to the notch 14.

(Modification 4)
As a cross-sectional shape in the notch part 14 of the heat conductive sheet 11 concerning the modification 4, and its vicinity, the shape shown to FIG. 5D is also possible. In FIG. 5D, the slit 20 in FIG. 5C penetrates the insulating sheet 13. In this case, even if air is taken in when the heat conductive sheet 11 is attached to, for example, a battery cell, air can be released from the slit 20, and the heat conductive sheet 11 can be closely attached to the battery cell.

  The other insulating sheet 13 may have a flat shape without the depression 18 at a location corresponding to the notch 14.

(Modification 5)
The shape shown to FIG. 6A is also possible as a plane shape in the notch part 14 of the heat conductive sheet 11 concerning the modification 5, and its vicinity. In FIG. 6A, the end of the notch 14 is rounded off.

(Modification 6)
The shape shown to FIG. 6B is also possible as a plane shape in the notch part 14 of the heat conductive sheet 11 concerning the modification 6, and its vicinity. In FIG. 6B, the end of the notch 14 has a semicircular shape.

(Modification 7)
The shape shown to FIG. 6C is also possible as a plane shape in the notch part 14 of the heat conductive sheet 11 concerning the modification 7, and its vicinity. In FIG. 6C, the end of the notch 14 has an angular shape.

  In addition, the shape by which the edge part of this notch part 14 was squared is not restricted to FIG. 6A-C, Various shapes are possible.

Second Embodiment
Next, a battery pack using the heat conduction sheet described in the first embodiment of the present disclosure will be described.

  FIG. 7 is a perspective view of a battery cell 21 which is a secondary battery using the heat conduction sheet 11 in the first embodiment. Moreover, FIG. 8 is sectional drawing which cut the battery cell 21 in the surface perpendicular | vertical to the main surface of the heat conductive sheet 11 containing the VIII-VIII line of FIG. The VIII-VIII line of FIG. 7 is a line segment along the longitudinal direction of the heat conductive sheet 11. FIG. 9 is a schematic view of a battery pack 22 constituted by the battery cells 21 shown in FIG.

  The battery pack 22 is configured by arranging and fixing a plurality of battery cells 21 in a metal housing 23. The size of the battery cell 21 is about 150 mm in width, about 100 mm in height, and about 20 mm in thickness. A heat conductive sheet 11 is attached to each battery cell 21. The battery cell 21 is a prismatic lithium ion battery, and its terminal electrode 24 is provided on the top surface. The heat conductive sheet 11 is bonded from one side surface of the battery cell 21 to the bottom surface. The bottom surface of the battery cell 21 is in contact with the housing 23 via the heat conductive sheet 11.

  The heat conductive sheet 11 is sealed by sandwiching the whole of the graphite sheet 12 with the insulating sheet 13. A plurality of notches 14 are arranged in a straight line on the graphite sheet 12 and are bent at portions where the notches 14 are arranged. The heat conductive sheet 11 is bonded to the battery cell 21 so that the bent portion of the heat conductive sheet 11 comes to the boundary (corner portion) between the side surface and the bottom surface of the battery cell 21. By doing so, the heat conductive sheet 11 can be easily bent in the area of the notch portion 14, and the heat conductive sheet 11 can be easily bonded from the side surface to the bottom surface of the battery cell 21. Therefore, the temperature distribution in the battery cell 21 can be reduced, and heat can be dissipated from the bottom surface of the battery cell 21 to the housing 23, whereby the entire temperature of the battery cell 21 can be lowered.

  The heat conductive sheet 11 may be bonded from one side surface of the battery cell 21 to the bottom surface and the other side surface. By doing this, the temperature distribution in the battery cell 21 can be further reduced.

  In the first and second embodiments, although the heat conduction sheet 11 is rectangular, it is not limited to a rectangle, but may be a polygon such as a triangle or a hexagon according to the shape of the battery cell 21, a circle or an ellipse, It may have a fan-like shape.

  Moreover, although the battery cell 21 was demonstrated as an example as said 2nd Embodiment, you may be except battery cell 21 as a heat generating body.

Third Embodiment
Next, a thermally conductive sheet according to a third embodiment of the present disclosure and a battery pack using the same will be described.

  FIG. 10 is a top view of the heat conduction sheet 15 in the third embodiment of the present disclosure. The difference between the heat conductive sheet 15 and the heat conductive sheet 11 according to the first embodiment is that the notches 14 are arranged in two rows. The arrangement of the notches 14 is provided corresponding to the lower corner of the battery cell 21 as described below. The material and cross-sectional structure which comprise the heat conductive sheet 15 are the same as that of the heat conductive sheet 11 demonstrated in 1st Embodiment. The heat conductive sheet 15 is bonded from one side surface of the battery cell 21 to the bottom surface and the other side surface. By doing this, the temperature distribution in the battery cell 21 can be further reduced.

  FIG. 11 is a perspective view of a battery cell 21 which is a secondary battery using a heat conductive sheet 15. 12 is a cross-sectional view of the battery cell 21 taken along a plane perpendicular to the main surface of the heat conductive sheet 15 including the XII-XII line of FIG. The XII-XII line of FIG. 11 is a line segment along the longitudinal direction of the heat conductive sheet 15. FIG. 13 is a schematic view of a battery pack 22 configured by the battery cell 21 shown in FIG.

  The battery pack 22 is configured by arranging and fixing a plurality of battery cells 21 in a metal housing 23. The size of the battery cell 21 is about 150 mm in width, about 100 mm in height, and about 20 mm in thickness. A heat conductive sheet 15 is bonded to each of the battery cells 21. The battery cell 21 is a prismatic lithium ion battery, and its terminal electrode 24 is provided on the top surface. The heat conductive sheet 15 is bonded from one side of the battery cell 21 to the bottom and the other side. The bottom surface of the battery cell 21 is in contact with the housing 23 via the heat conductive sheet 15.

  The heat conductive sheet 15 is sealed by sandwiching the whole of the graphite sheet 12 with the insulating sheet 13. A plurality of notches 14 are arranged in a straight line on the graphite sheet 12 and are bent at portions where the notches 14 are arranged. The heat conductive sheet 15 is bonded to the battery cell 21 so that the bent portion of the heat conductive sheet 15 comes to a boundary (corner portion) between the two side surfaces and the bottom surface of the battery cell 21. By doing so, the heat conduction sheet 15 can be easily bent in the area of the notch portion 14, and the heat conduction sheet 15 can be easily bonded from the side surface to the bottom surface of the battery cell 21. Therefore, the temperature distribution in the battery cell 21 can be reduced, and heat can be dissipated from the bottom surface of the battery cell 21 to the housing 23, whereby the entire temperature of the battery cell 21 can be lowered.

  In the first to third embodiments, the heat conductive sheet 11 or the heat conductive sheet 15 has a rectangular shape, but the shape is not limited to a rectangular shape, and may be a triangle, a hexagon or the like according to the shape of the battery cell 21. It may be a polygon, or it may have a circle, an ellipse, or a sector shape.

  Moreover, the number of the notch part 14 in the heat conductive sheet 11 or the heat conductive sheet 15 may be 1, and may be 2 or more. For example, a recess that does not penetrate may be provided instead of the notch 14. The shape of the notch portion 14 viewed from the top surface of the heat conductive sheet 11 or the heat conductive sheet 15 is not limited to the shape of a rectangle or FIGS. 6A to 6C, and may be a polygon such as triangle, pentagon or hexagon. It may be a shape in which they are connected.

  Moreover, the magnitude | size of the heat conductive sheet 11 of this indication or the heat conductive sheet 15 is not limited to the case of the said embodiment, Various sizes are possible.

  Moreover, although PET was demonstrated to the example as the insulating sheet 13, it is also possible to use not only PET but heat resistant resin like polyimide.

  Moreover, when the insulation sheet 13 is PET, it is also possible to crimp the insulation sheets 13 by heat.

  Moreover, although the battery cell 21 was demonstrated as an example as said 2nd and 3rd embodiment, you may be except battery cell 21 as a heat generating body. For example, even in the case of an IC chip mounted on a smartphone, the heat conduction sheet of the present disclosure can be used. Moreover, the heat conduction sheet of this indication can be used also to the power module which is a heat-emitting component.

  The heat conduction sheet 11 or 15 is formed by sealing the graphite sheet 12 with the insulation sheet 13 interposed therebetween, and as an example of the sealing method, two sheets of insulation are provided as shown in FIG. The entire graphite sheet 12 may be sandwiched by the sheet 13. As another example of the sealing method, as shown in FIG. 15, a graphite sheet is placed on one large insulating sheet, and the insulating sheet is folded at the long side or the short side of the graphite sheet. The graphite sheet may be sandwiched.

  The thermally conductive sheet according to the present disclosure and the battery pack using the same can be easily extended from one surface of the battery cell to another surface orthogonal to the other even when insulating sheets are bonded to both surfaces of a graphite sheet as the thermally conductive sheet. Can be attached to Thus, a highly reliable battery pack can be obtained, which is industrially useful.

DESCRIPTION OF SYMBOLS 11, 15 Thermal conduction sheet 12 Graphite sheet 13 Insulating sheet 14 Notch part 16 Recess 17 Through hole 18 hollow 19 Groove 20 Slit 21 Battery cell 22 Battery pack 23 Case 24 terminal electrode

Claims (5)

  What is claimed is: 1. A thermally conductive sheet, wherein the whole of the graphite sheet is sealed by being sandwiched by insulating sheets, and the plurality of notches are arranged in a straight line in the graphite sheet. When the length in the direction in which the notches are arranged is L, and the length between the notches and the notches is S,

The heat conduction sheet according to claim 1, characterized in that:   The heat conductive sheet according to claim 1, wherein the insulating sheets are joined to each other inside the notched portion. Assuming that the width of the notched portion in a direction perpendicular to the direction in which the notched portion is arranged is W, the thickness of the graphite sheet is T1, and the thickness of the insulating sheet is T2.

The heat conduction sheet according to claim 1, characterized in that:   A secondary battery pack holding a plurality of secondary battery cells in a housing, wherein the heat conduction sheet according to claim 1 is bent at a portion where the plurality of notches are arranged, and the secondary The heat conductive sheet is abutted from the side surface to the bottom surface of the battery cell, and the heat conductive sheet is in such a manner that the bent portion of the heat conductive sheet comes to the boundary between the side surface and the bottom surface of the secondary battery cell A secondary battery pack characterized in that is disposed.

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